SAW Resonator Aperture Layout for Steeper Filter Skirts
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Solution Overview
Problem
Designing acoustic wave filters with a steep filter skirt is challenging, particularly for surface acoustic wave (SAW) filters, as they often struggle to meet specifications for steepness near the passband due to transverse spurious modes, which are difficult to suppress without increasing circuit complexity or area consumption.
Innovation Solution
The use of series and shunt acoustic wave resonators with narrow and wide interdigital transducer electrode apertures, respectively, to concentrate transverse spurious modes at specific frequencies, thereby increasing the steepness of the filter skirt without additional circuit components, and incorporating temperature compensation to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional SAW filter designs are used, then the filter structure is simple, but the filter skirt steepness is insufficient
Solution Approach 1:
The patent changes the physical parameters of the interdigital transducer electrodes by implementing different aperture widths (narrow vs. wide) for series and shunt resonators. This parameter variation enables the concentration of transverse spurious modes at specific frequencies, achieving steep filter skirts without adding circuit complexity. The series resonators use narrow apertures while shunt resonators use wide apertures, creating the desired frequency-selective behavior.
2Manufacturing precision
If transverse spurious modes are suppressed using conventional methods, then mode concentration improves, but circuit complexity or area consumption increases
Solution Approach 1:
The patent applies local quality by giving different aperture characteristics to different parts of the filter circuit. Series resonators are equipped with narrow-aperture interdigital transducer electrodes while shunt resonators use wide-aperture electrodes. This localized differentiation enables each resonator type to contribute differently to the overall filter response, concentrating transverse spurious modes where needed without increasing overall circuit complexity.
3Manufacturing precision
If narrow aperture resonators are used, then transverse spurious modes are concentrated, but Ohmic loss increases
Solution Approach 1:
The patent segments the filter into two distinct resonator types with different aperture characteristics. Narrow-aperture series resonators concentrate transverse spurious modes, while wide-aperture shunt resonators provide lower Ohmic loss paths. This segmentation allows the system to benefit from both narrow and wide aperture characteristics, achieving mode concentration while managing energy loss through the distributed resonator architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a steeper filter skirt with improved quality factor and reduced Ohmic loss, achieving low insertion loss and high rejection of frequencies close to the passband without external circuit components, thus enhancing the performance of SAW filters.
Implementation Method 1
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer
Implementation Method 2
The plurality of series acoustic wave resonators and the plurality of shunt acoustic wave resonators are together arranged to filter a radio frequency signal
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave filter with an acoustic wave resonator arranged to concentrate a transverse spurious mode at a frequency. Such an acoustic wave resonator can have a narrow aperture to concentrate the transverse spurious mode. The transverse spurious mode can increase steepness of a skirt of the acoustic wave filter. Related methods, acoustic wave devices, multiplexers, radio frequency front ends, radio frequency modules, and wireless communication devices are disclosed.